Journal of Pharmacological and Toxicological Methods
Original articlePulmonary function assessment by whole-body plethysmography in restrained versus unrestrained mice
Introduction
Pulmonary function and pulmonary physiological parameters are important study endpoints in the pharmaceutical and toxicological sciences. For example, studies of drugs to treat asthma (Mauser et al., 1995), evaluations of toxicological properties of inhaled xenobiotics Barrow et al., 1977, Schaper et al., 1985, and investigations of allergic airway reactions Chand et al., 1993, Lambert et al., 1999 all rely on pulmonary endpoints such as changes in respiratory rate, tidal and minute volumes, and bronchoconstriction resulting from specific antigens or nonspecific agents such as methacholine.
In the 1950s, transpulmonary pressure and inspiratory and expiratory flows were directly measured on anesthetized and ventilated animals (Amdur & Mead, 1958). However, these physiological measurements involved invasive surgical procedures and were confounded by the effect of anesthesia. Because these procedures were terminal, they did not allow for repeated assessments using the same animal and therefore required large numbers of animals. These restrictions led to the use of a noninvasive airway mechanics (NAM) plethysmograph in the late 1970s (Pennock, Cox, Rogers, Cain, & Wells, 1979). The NAM plethysmograph is a double-chambered instrument in which the animal is restrained at the neck with an airtight rubber collar to isolate the thoracic cavity. This design allows for accurate and direct measurements of inspiratory and expiratory flows, tidal volume, minute volume, and respiratory rate. Since there is no measurement of transpulmonary pressure, airway resistance is extrapolated from the lag between the airflow in the thoracic and nasal chambers and is reported as specific airway resistance (sRaw) (Agrawal, 1981). While the double chamber plethysmograph allows for repeated measurements on the same animal and is noninvasive, long-term physiological evaluations cannot be performed due to the stress of the neck collar restraint. Concern regarding the effect of an airtight neck seal on airway resistance has also been raised (Pennock et al., 1979).
More recently, an unrestrained single chamber whole-body plethysmograph has been designed for use in pharmaceutical and toxicological studies. In this instrument, no restraint is required, and the animal can have free access to food and water. Therefore, physiological measurements can be made for extended time periods (~24 h), which is useful for examining late-phase bronchoconstrictive events associated with animal models of asthma Cieslewicz et al., 1999, Uchida et al., 1996. The major drawbacks of the single chamber plethysmograph are that inspiratory and expiratory flows are indirectly measured and transpulmonary pressure is not determined. Instead, physiological measurements are based on pressure changes in the single chamber plethysmograph due to the addition of heat and water vapor in the inhaled air (Drorbaugh & Fenn, 1955). Airway resistance is extrapolated as the enhanced pause (Penh) upon exhalation due to bronchoconstriction (Hamelmann et al., 1997). Since the WBP does not directly measure any of the physiological parameters previously described by Amdur and Mead (1958), measurements made with the WBP may be misleading (Mitzner & Tankersley, 1998). Previous studies in guinea pigs and mice have shown that Penh is a valid measurement of airway resistance Chong et al., 1998, Hamelmann et al., 1997; however, there is little information regarding the accuracy and precision of physiological measurements such as respiratory rate and tidal volume in the single chamber plethysmograph. Therefore, the objective of the present study was to utilize both the single and double chamber plethysmographs and mice strains with known interstrain differences in airway physiology to (1) determine the reproducibility of physiological data from repeated tests on the same animal in both plethysmographs and (2) compare physiological data measured in the same animals between the two plethysmographs to ensure that both instruments produce repeatable and reliable data.
Section snippets
Animals
Pathogen free female mice weighing 15–20 g obtained from commercial suppliers (BALB/c, B6C3F1, and CD-1 from Charles River, Raleigh, NC; A/J from Jackson Laboratory, Bar Harbor, ME) were used for this study and acclimated to the facility for 14 days prior to experiments. Animals were housed in polycarbonate cages with direct cellulose bedding (Alpha-dri, Shepherd Special Papers, Kalamazoo, MI) and had access to food (NIH07, Zieglar Bros., Lancaster, PA) and deionized water ad libitum. Mice were
Evaluation of repeated measurements with the single and double chamber plethysmographs
Upon comparison of the baseline physiological data of all four mice strains obtained on two different occasions in the double chamber plethysmograph, only the CD-1 mice demonstrated significantly elevated sRaw values (3.37±0.69, n=4) on the second experimental run when compared with the other three strains. Comparison of all other measurements on the mice strains demonstrated no significant differences between experimental runs (Table 1). Comparison of the baseline physiological data of all
Discussion
In the present study, we compared pulmonary physiological parameters obtained from two commonly used whole-body plethysmographs in mice with known interstrain differences in pulmonary physiology. Both the single and double chamber plethysmographs generated reproducible physiological parameters such as respiratory rate, tidal volume, and inspiratory and expiratory times. However, comparison of baseline physiological measurements between the two plethysmographs demonstrated significant
Acknowledgements
The authors would like to thank Mr. Earl Tewksbury and Mr. Carl Parkinson for their help with the aerosol delivery system, and Mr. Dennis House for his help with the statistical analysis.
References (23)
Specific airway conductance in guinea pigs: normal values and histamine induced fall
Respiration Physiology
(1981)- et al.
Measurement of bronchoconstriction using whole-body plethysmograph: comparison of freely moving versus restrained guinea pigs
Journal of Pharmacological and Toxicological Methods
(1998) - et al.
A theoretical analysis of the barometric method for measurement of tidal volume
Respiration Physiology
(1978) - et al.
Residual oil fly ash exposure enhances allergic sensitization to house dust mite
Toxicology and Applied Pharmacology
(1999) - et al.
A method to classify airborne chemicals which alter the normal ventilatory response induced by co2
Toxicology and Applied Pharmacology
(1985) - et al.
Mechanics of respiration in unanesthetized guinea pigs
American Journal of Physiology
(1958) - et al.
Comparison of the sensory irritation response in mice to chlorine and hydrogen chloride
Archives of Environmental Health
(1977) - et al.
Phosphatidylcholine molecular species in lung surfactant. Composition in relation to respiratory rate and lung development
American Journal of Respiratory Cell and Molecular Biology
(2001) - et al.
Cholinesterase activity is similar in C3H/HeJ and A/J mice and does not account for their different bronchoconstrictor responsiveness
Experimental Lung Research
(1999) - et al.
Aeroallergen-induced dyspnea in freely moving guinea pigs: quantitative measurement by bias flow ventilated whole body plethysmography
Allergy
(1993)
The late, but not early, asthmatic response is dependent on IL-5 and correlates with eosinophil infiltration
Journal of Clinical Investigation
Cited by (96)
The regulation of circRNA_kif26b on alveolar epithelial cell senescence via miR-346-3p is involved in microplastics-induced lung injuries
2023, Science of the Total EnvironmentLow-dose intrapulmonary drug delivery device for studies on next-generation therapeutics in mice
2023, Journal of Controlled ReleaseGlabridin attenuates airway inflammation and hyperresponsiveness in a mice model of ovalbumin-induced asthma
2020, Pulmonary Pharmacology and TherapeuticsCitation Excerpt :Song et al. reported that Penh value increased significantly in asthmatic rat models induced by OVA [29]. It has been determined that Penh value in mice exposed to the MCh challenge produced more reliable and reproducible results in single-chamber plethysmography compared to double-chamber plethysmography [30]. Glabridin (20 or 30 mg/kg) reduced significantly the Penh values which increased in the OVA group, but that of low dose glabridin (10 mg/kg) was insignificant.
Inhale, exhale: Why particulate matter exposure in animal models are so acute?
2019, Environmental Pollution